bcachefs: Add a missing btree_path_make_mut() call

Also add another small helper, btree_path_clone().
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>

fs/bcachefs/btree_iter.c

@@ -1491,16 +1491,22 @@ static void btree_path_copy(struct btree_trans *trans, struct btree_path *dst,
 	trans->paths_sorted = false;
 }
 
-struct btree_path * __must_check
-__bch2_btree_path_make_mut(struct btree_trans *trans,
-			 struct btree_path *path, bool intent)
+static struct btree_path *btree_path_clone(struct btree_trans *trans, struct btree_path *src,
+					   bool intent)
 {
-	struct btree_path *new = btree_path_alloc(trans, path);
+	struct btree_path *new = btree_path_alloc(trans, src);
 
-	btree_path_copy(trans, new, path);
+	btree_path_copy(trans, new, src);
 	__btree_path_get(new, intent);
+	return new;
+}
+
+struct btree_path * __must_check
+__bch2_btree_path_make_mut(struct btree_trans *trans,
+			   struct btree_path *path, bool intent)
+{
 	__btree_path_put(path, intent);
-	path = new;
+	path = btree_path_clone(trans, path, intent);
 	path->preserve = false;
 #ifdef CONFIG_BCACHEFS_DEBUG
 	path->ip_allocated = _RET_IP_;
@@ -2030,6 +2036,8 @@ struct bkey_s_c bch2_btree_iter_peek(struct btree_iter *iter)
 
 	cmp = bpos_cmp(k.k->p, iter->path->pos);
 	if (cmp) {
+		iter->path = bch2_btree_path_make_mut(trans, iter->path,
+					iter->flags & BTREE_ITER_INTENT);
 		iter->path->pos = k.k->p;
 		trans->paths_sorted = false;
 	}